iOS/Android/Web: From splitting the check at a restaurant to splitting the cable bill with your roommates, you can rack up a lot of IOUs in day-to-day life. Splitwise helps you manage them with a simple ledger, and lets you pay back your debts via PayPal.

We've mentioned Splitwise a few times before, but it's matured a lot in the past year or so. Now it's a fully-fledged IOU manager, helping you and your friends keep all your debts straight and easily payable. You can add individual friends from your address book or set up a group, like your housemates (They don't need to be Splitwise members for you to manage your IOUs, but it's a lot more useful if they are). It even has a handy check splitter, perfect for when you're out at a restaurant and don't want to do the math yourself (though sadly, only the web version lets you split the check item-by-item). And, when you want to settle your payments, you can just send a quick PayPal payment to your friends right from Splitwise. It may seem like overkill for the occasional lunch or after-work drink, but if you share expenses with your friends often, it can be a good way to keep track of who owes money to whom.